A slip control system for a motor vehicle controls slips in driving wheels and includes a sensor for detecting a slip ratio of each driving wheel and a traction control system for decreasing a slip of each driving wheel by controlling a driving force transmitted to each driving wheel so that the slip ratio of each driving wheel is at least equal to a predetermined desired slip ratio when the slip ratio of the driving wheel becomes equal to the desired slip ratio. An automatic transmission control system controls an automatic transmission by using a first shift property for a normal operation, and a second shift property for a traction control operation which is adapted to determine a relative higher speed stage. A device is provided for switching the first shift property to the second shift property when the traction control operation is started by the traction control system.